slartv.f

Go to the documentation of this file.

*> \brief \b SLARTV applies a vector of plane rotations with real cosines and real sines to the elements of a pair of vectors.
*
*  =========== DOCUMENTATION ===========
*
* Online html documentation available at
*            http://www.netlib.org/lapack/explore-html/
*
*> Download SLARTV + dependencies
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/slartv.f">
*> [TGZ]</a>
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/slartv.f">
*> [ZIP]</a>
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/slartv.f">
*> [TXT]</a>
*
*  Definition:
*  ===========
*
*       SUBROUTINE SLARTV( N, X, INCX, Y, INCY, C, S, INCC )
*
*       .. Scalar Arguments ..
*       INTEGER            INCC, INCX, INCY, N
*       ..
*       .. Array Arguments ..
*       REAL               C( * ), S( * ), X( * ), Y( * )
*       ..
*
*
*> \par Purpose:
*  =============
*>
*> \verbatim
*>
*> SLARTV applies a vector of real plane rotations to elements of the
*> real vectors x and y. For i = 1,2,...,n
*>
*>    ( x(i) ) := (  c(i)  s(i) ) ( x(i) )
*>    ( y(i) )    ( -s(i)  c(i) ) ( y(i) )
*> \endverbatim
*
*  Arguments:
*  ==========
*
*> \param[in] N
*> \verbatim
*>          N is INTEGER
*>          The number of plane rotations to be applied.
*> \endverbatim
*>
*> \param[in,out] X
*> \verbatim
*>          X is REAL array,
*>                         dimension (1+(N-1)*INCX)
*>          The vector x.
*> \endverbatim
*>
*> \param[in] INCX
*> \verbatim
*>          INCX is INTEGER
*>          The increment between elements of X. INCX > 0.
*> \endverbatim
*>
*> \param[in,out] Y
*> \verbatim
*>          Y is REAL array,
*>                         dimension (1+(N-1)*INCY)
*>          The vector y.
*> \endverbatim
*>
*> \param[in] INCY
*> \verbatim
*>          INCY is INTEGER
*>          The increment between elements of Y. INCY > 0.
*> \endverbatim
*>
*> \param[in] C
*> \verbatim
*>          C is REAL array, dimension (1+(N-1)*INCC)
*>          The cosines of the plane rotations.
*> \endverbatim
*>
*> \param[in] S
*> \verbatim
*>          S is REAL array, dimension (1+(N-1)*INCC)
*>          The sines of the plane rotations.
*> \endverbatim
*>
*> \param[in] INCC
*> \verbatim
*>          INCC is INTEGER
*>          The increment between elements of C and S. INCC > 0.
*> \endverbatim
*
*  Authors:
*  ========
*
*> \author Univ. of Tennessee
*> \author Univ. of California Berkeley
*> \author Univ. of Colorado Denver
*> \author NAG Ltd.
*
*> \ingroup lartv
*
*  =====================================================================
      SUBROUTINE slartv( N, X, INCX, Y, INCY, C, S, INCC )
*
*  -- LAPACK auxiliary routine --
*  -- LAPACK is a software package provided by Univ. of Tennessee,    --
*  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
*
*     .. Scalar Arguments ..
      INTEGER            INCC, INCX, INCY, N
*     ..
*     .. Array Arguments ..
      REAL               C( * ), S( * ), X( * ), Y( * )
*     ..
*
*  =====================================================================
*
*     .. Local Scalars ..
      INTEGER            I, IC, IX, IY
      REAL               XI, YI
*     ..
*     .. Executable Statements ..
*
      ix = 1
      iy = 1
      ic = 1
      DO 10 i = 1, n
         xi = x( ix )
         yi = y( iy )
         x( ix ) = c( ic )*xi + s( ic )*yi
         y( iy ) = c( ic )*yi - s( ic )*xi
         ix = ix + incx
         iy = iy + incy
         ic = ic + incc
   10 CONTINUE
      RETURN
*
*     End of SLARTV
*
      END